To avoid cross infections, the flow sensor is designed as a sensor that can be disinfected and/or replaced in devices known from the state of the art for detecting a gas volume flow by means of a flow sensor, especially in medical devices with a flow sensor. In an inexpensive device for detecting a gas volume flow, the ultrasound transmitter and the ultrasound receiver must therefore be separated from the flow sensor for the replacement of the flow sensor.
An ultrasound spirometer, which has a replaceable flow sensor, is known from DE 42 22 286 C1; the flow sensor has a measuring tube, into which a sterile, easy-to-replace tube can be inserted in an accurately fitting manner. The sterile tube is inserted in an accurately fitting manner and has at a transition to an ultrasound measuring window, which is permeable to sound waves but extensively impermeable to microorganisms and other contaminants. The measuring windows may be formed by a foam, by an elastomer, or by a very thin plate, especially a Mylar film.
A device for measuring the flow velocity of a gas in a medical application by means of ultrasound run time measurement with a measuring tube and two ultrasound converters that can be inserted into the measuring tube is known from DE 101 56 854 A1. The ultrasound converters are separated from an interior space of the measuring tube by means of membranes. The membranes are of a gas-tight design according to the present invention and inserted into the measuring tube such that the latter forms a gas-tight tube connection. The ultrasound converters separably connected to the measuring tube have a flush contact with the membranes.
Devices known from the state of the art with a flow sensor for detecting a gas volume flow have ultrasound converters, which can detect a flow velocity of the gas flow, especially by means of doppler interferometry. The device may comprise for this an analysis unit, which is connected to the ultrasound transmitter and the ultrasound receiver and is designed to detect a sound wavelength and/or sound run time of an ultrasound transmitted by the ultrasound transmitter and received by the ultrasound receiver.